half to float intrinsic promotion

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#1

Hi Guys,

I am trying to promote half to float for my intrinsic math operations,
following class and pattern are defined.

"

class S_HF__HF< string asmstr> : Intrinsic
<[llvm_float_ty ], [llvm_float_ty ],
[IntrNoMem],
!strconcat(asmstr, “_f16”)>;

def :Pat<( f16 (int_my_math_f16 f16:$src)), (F2Hsr (FEXTsr f16:$src) )>;

“
where FEXTsr is implementing the fextend type profile, F2Hsr is implementing as the float to half conversion .
“int_my_math_f16” is implementing the “S_HF__HF” profile above.
I am just trying to
(1) convert the $src from f16 to f32 using FEXTsr.
(2) use the F2Hsr to convert the f32 back to f16.
for testing.
however, I always got the error
”
Type inference contradiction found, merging ‘f32’ into ‘f16’
def :Pat<( f16 (int_my_math_f16 f16:$src)), (F_2_F16sr (FEXTsr f16:$src) )>;

“

Wondering what is the reason? I noticed that LLVM does not have the intrinsic type “LLVM_f16_ty”, so I always use “LLVM_float_ty” for it as long as it is a float or half.

best

Kevin

#2

Hi Guys,

I am trying to promote half to float for my intrinsic math operations,
following class and pattern are defined.

"
class S_HF__HF< string asmstr> : Intrinsic
        <[llvm_float_ty ], [llvm_float_ty ],
[IntrNoMem],
!strconcat(asmstr, "_f16")>;

def :Pat<( f16 (int_my_math_f16 f16:$src)), (F2Hsr (FEXTsr f16:$src) )>;

“
where FEXTsr is implementing the fextend type profile, F2Hsr is
implementing as the float to half conversion .
“int_my_math_f16” is implementing the “S_HF__HF” profile above.
I am just trying to
(1) convert the $src from f16 to f32 using FEXTsr.
(2) use the F2Hsr to convert the f32 back to f16.
for testing.
however, I always got the error
”
Type inference contradiction found, merging 'f32' into 'f16'
def :Pat<( f16 (int_my_math_f16 f16:$src)), (F_2_F16sr (FEXTsr f16:$src) )>;

“

Wondering what is the reason? I noticed that LLVM does not have the
intrinsic type “LLVM_f16_ty”, so I always use “LLVM_float_ty” for it as long
as it is a float or half.

Hi Kevin,

In "llvm_float_ty", "float" means f32 (as in the IR language
reference, and as defined in include/llvm/IR/Intrinsics.td). So in
your example, TableGen complains because you're feeding an f16 to an
intrinsic declared as taking an f32.

However, there's also "llvm_half_ty" in Intrinsics.td, corresponding
to f16; why not use that instead?

-Ahmed

#3

Thank you very much!
don’t know why I just overlooked the llvm_half_ty when I was reading the intrinsics.td

best

kevin

#4

Hi Guys,

I am trying to promote half to float for my intrinsic math operations,
following class and pattern are defined.

"
class S_HF__HF< string asmstr> : Intrinsic
        <[llvm_float_ty ], [llvm_float_ty ],
  [IntrNoMem],
  !strconcat(asmstr, "_f16")>;

def :Pat<( f16 (int_my_math_f16 f16:$src)), (F2Hsr (FEXTsr f16:$src) )>;

“
where FEXTsr is implementing the fextend type profile, F2Hsr is implementing as the float to half conversion .
“int_my_math_f16” is implementing the “S_HF__HF” profile above.
I am just trying to
(1) convert the $src from f16 to f32 using FEXTsr.
(2) use the F2Hsr to convert the f32 back to f16.
for testing.
however, I always got the error
”
Type inference contradiction found, merging 'f32' into 'f16'
def :Pat<( f16 (int_my_math_f16 f16:$src)), (F_2_F16sr (FEXTsr f16:$src) )>;

“

Wondering what is the reason? I noticed that LLVM does not have the intrinsic type “LLVM_f16_ty”, so I always use “LLVM_float_ty” for it as long as it is a float or half.

There is llvm_half_ty. Try defining your intrinsic with that instead of
llvm_float_ty.

-Tom